The Lorentz Transformation, which is considered as constitutive for the Special Relativity Theory, was invented by Voigt in 1887, adopted by Lorentz in 1904, and baptized by Poincare in 1906. Einstein probably picked it up from Voigt directly.It is true that Voigt had a scaled version of the Lorentz transformation before anyone else. See History of Lorentz transformations for details.
Einstein like Poincare was convinced of the validity of the generalized relativity princi-ple. In his famous paper of 1905 6 he raised this conjecture to a postulate and claimed that he could derive the Lorentz Transformation by using a second postulate, namely “that light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body”. A careful analysis of §3 of his paper shows, however, that he worked on the same assumption as Voigt, namely that the velocity of light is constant for any moving observer. ...OIt seems much more likely to me that Einstein got the transformation from Lorentz, as Einstein follows the spirit of Lorentz's work rather closely.
It is likely that Einstein, who did not quote anybody in Ref. 5, found his trans-formation directly in Voigt’s paper of 1897. In the monograph of 1913 (Ref. 3) he assures us that he was not aware of Lorentz’s paper of 1904. This is credible, as he did not use Lorentz’s nomenclature (x, y, z, t) <-> (x', y', z', t'), but he adopted Voigt’s: (x, y, z, t) <-> (ξ, η, ζ, τ). ...
Einstein kept denying that the Michelson-Morley experiment had any influence on the development of his theory7. Probably he had read a paper with the title Theory of light for moving media by W. Voigt8 which appeared two months later than Ref. 1 in the same Journal. On page 233 Voigt analyzes the Michelson experiment and comes to the conclusion:
“It follows that the observed results in the experimental set-up that was chosen by Mr. Michelson are entirely independent of any translation. Hence, Mr. Michelson obtained the negative results which he factually obtained with necessity, regardless whether the ether moves with the earth or not.”
The Michelson-Morley experiment was crucial for Lorentz, but not for Einstein. That is because they had different viewpoints. Lorentz was creating relativity theory out of the experimental evidence, and convincing the physics community that his outrageous conclusions were correct. Einstein's view was the reverse. His famous 1905 paper postulated the conclusions of Lorentz's theory, and gave an exposition of Lorentz's relativity. That is why Einstein ignored the physical evidence.